Electronics systems, such as communication systems, radar systems, infrared sensor systems, laser tracking systems, or directed energy systems, whether ground based, mobile, airborne, shipboard, or spacecraft based, generally have several subsystems that are provided power from a power source over an electric power bus. Certain subsystems may draw a ripple current from the power source that may affect the other subsystems. Several specifications, such as MIL STD 461, address the quantity and frequency content of ripple current that may be reflected to an electric power bus, in addition to other EMC requirements.
For example, in the case of certain types of sensor systems, a cryogenic cooler electronics control system may draw 10 amps or more of ripple current at a nominal frequency between 70 and 100 Hz from the electric power bus. In some applications, such as a satellite system, this large ripple current draw may destabilize the bus and may degrade the performance of other electronics subsystems using the bus, particularly those managing low power sensor signals. For another example, in the case of a laser system that generates pulsed output energy, or a directed energy system that generates pulses of RF energy, the current required for the pulsed output may similarly reflect back to an electric power bus, and may destabilize the electric power bus.
Conventional approaches to reduce the ripple current on an electric power bus utilize low frequency low pass passive filters with large capacitors and inductors. However, the size and weight of the large capacitors and inductors required for low frequency low pass filter bandwidth make these approaches undesirable for applications where size and/or weight are important factors. Other conventional approaches include the use of shunt regulators in parallel with the fluctuating load. These shunt regulators draw load current under light load conditions and reduce shunt power under system heavy load conditions, thus keeping the net current draw from a power source constant.
Thus, there are needs for controls and methods that control power converter current accurately on a pulse-by-pulse basis using average current mode control. There are also needs for systems and methods that control and regulate input current drawn from an electric power bus. There are also needs to attenuate ripple current reflected to an electric power bus.